A vector potential is not a scalar quantity such as an electricpotential, but rather a potential that has direction and is a concept that integrates electric fields and magnetic fields.
However, when a vector potential actually appears, because it is accompanied by an electric field or a magnetic electric field, there has been discussion in the past that a vector potential is not a physical quantity, but rather a product of the mathematics. The issue was ultimately resolved by the late Dr. Tomura of Hitachi Ltd., who elegantly demonstrated the theoretical prediction known as the Aharonov-Bohm Effect by an electron beam interference experiment. The results of the experiment verified that a vector potential changes the phase of an electron wave. If, rather than controlling an electric field or a magnetic field, a vector potential can be controlled, new possibilities are opened up for electromagnetic applications.
Conventionally, in order to generate a vector potential, a device has been constituted with a wire wound in the form of a coil, and the magnetic field has had a relatively simple path. For this reason, the vector potential had been placed so that it rotated about the magnetic lines as a center. If electric manipulation was attempted, a magnetic field always appeared (refer to, for example Japanese Patent Application Publication No. 1999-347135).
Also, conventionally, in order to generate an electric field in space, electrodes are brought into mutual opposition, and an electric field between electrodes of a so-called capacitor has been used. In this case, because metal electrodes are directly exposed to the outside, there have been cases in which corrosion and discharge occurred due to the surrounding atmosphere. Because of the capacitor structure, the load impedance becomes capacitive, the impedance increases, and impedance matching becomes difficult. In addition, because the electrodes are exposed, there has been a danger of electrical shock by high voltage.
Next, in a case in which a conductive medium is placed inside an electric field when conventionally time varying magnetic field has been applied to a conductor, an eddy current is generated in a circle. Since induced-current always flows as eddy-current in conductive medium when a magnetic field is applied, it is difficult to apply an electric current linearly in the specific point.
Additionally, in a conventional transformer using a conductive wire as the electrically conductive medium, because a magnetic field leaks from the primary coil, there had been cases in which other apparatuses were adversely affected. In particular, with electron beam apparatuses that draw microfine patterns, and medical apparatuses that cannot be allowed to malfunction and moving transport equipment, strict magnetic shielding has become necessary.